A `@preconcurrency` conformance to an inherited protocol should imply
`@preconcurrency` on its parents as well. For example:
```swift
protocol Parent {
func a()
}
protocol Child: Parent {
func b()
}
@MainActor
class Test: @preconcurrency Child {
func a() {
}
func b() {
}
}
```
`Test` conformance to `Parent` implied by its conformance to `Child`
should carry `@preconcurrency` and inject dynamic actor isolation checks
to witness of `a()`.
Resolves: https://github.com/apple/swift/issues/74294
Resolves: rdar://129599097
